The Total Synthesis of the (±)-Bourbonenes

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

“…Plenty of examples have been reported in the literature. [79][80][81][82][83][84][85][86][87] The approach from the less shielded face is favored and there are no significant exceptions to this rule. In this regard the stereochemical outcome of photocycloadditions to chiral alkenes is more readily predictable than the one of photocycloadditions of chiral alkenones.…”

“…The cyclobutane ring is part of many natural products and it is therefore not surprising that [2+2]-photocycloaddition reactions have been employed to get access to these targets. Pioneering efforts were dedicated to the syntheses of caryophyllene, 97 the bourbounenes 79,98 and annotine. 99 Another naturally occurring cyclobutane which has aroused considerable synthetic attention is the boll weevil pheromone grandisol 52.…”

Frontier-controlled pericyclic reactions of powerful electron-attracting cyclic dienones and diazadienones with 1H-azepine: molecular structures of cycloadducts and some comments

“…Cycloaddition Reaction of Id with 2a. Thermolysis of l,3-bis(diazo)-l,3-diphenyl-2-propanone (8) provided a simple route to 2,5-diphenyl-3,4-diazacyclopentadienone (Id) which is obtained as a convenient and a powerful electron-deficient heterodiene component in spite of an unstable intermediate (Scheme III). Indeed, this fascinating intermediate has been shown to act as both a dienophile with 2,3-dimethyl-1,3-butadiene and a diene with norbornene in the pericyclic reactions.14 These interesting features of the pericyclic reactions of diazacyclopentadienone Id prompted us to examine the model of cycloaddition of 8 with N-(ethoxycarbonyl) azepine (2a):…”

“…However, the reactions of cycloalkenones (cyclohexenone, cyclopentenone) with simple unsymmetrical olefins often give rise to complications. While examples of such reactions are less numerous in the literature-presumably due to complications involved in the separation and characterization of the products-an ample number of reports attests to the low regioselectivity of the reaction.5, 8,12,13 In spite of the problem of mixtures of regioisomers encountered in some reactions, the utility of these reactions in some lengthy synthetic procedures5 attests to the power of the synthetic method.…”

Cyclobutanes in organic synthesis. Part I. Fragmentation to 1,4-dicarbonyl compounds. General considerations

“…The n.m.r. spectrum showed signals at 8.9 (6H), 7.88 (3H), 7.8 (2H), 7.75 (2H, d), 6.85 (2H), and 3 . 4 5~ ( l H , t).…”